Jierong Ying

Preparation of V-LiFePO4 cathode material for Li-ion batteries

The preparation of vanadium-modified olivine LiFePO4 was attempted using vanadium-modified FePO4 precursor which was synthesized by controlled crystallization. The structure and electrochemical behavior of V-LiFePO4 with different vanadium contents were investigated. The electrochemical behavior of V-LiFePO4 materials at high rate and low temperature was compared with that of the LiFePO4 material. Incorporation of vanadium improved the electrochemical performance of LiFePO4. The investigation showed that the 3%V-modified LiFePO4 presented the best electrochemical performance.

Preparation and Characterization of LiFePO4 from a Novel Precursor of NH4FePO4 ∙ H2O

The crystal structure of the electrochemical material, such as grain size and crystal lattice defects, influences its character directly. LiFePO 4 cathode material was obtained by solid-state reaction of the homogeneous mixture, NH 4 FePO 4 ·H 2 O, Li 2 CO 3 , and sugar. The influences of the reaction temperature, content of carbon on the structure, and electrochemical performance of LiFePO 4 were investigated. The X-ray diffraction characterization, scanning electron microscopy, and electrochemical performance measurements were carefully studied. The relationship between grain size and the electrochemical performance is discussed. As a result, the LiFePO 4 cathode material with 5% carbon obtained by sintering at 600°C for 12 h has good electrochemical performance. Between 2.5 and 4.2 V vs Li, a reversible capacity is as high as 162 mAh g -1 at 0.05 C.

Preparation of Li3V2 (PO4)3/LiFePO4 composite cathode material for lithium ion batteries

A novel process was attempted for synthesis of Li3V2 (PO4)3/LiFePO4 composite cathode material via loading nano-LiFePO4 (LFP) powders onto the outside of micrometer-size spherical Li3V2 (PO4)3 (LVP). The precursor of nano-LFP and LVP were synthesized via “controlled crystallization” and “spray drying” techniques, respectively. The X-ray diffraction characterization, scanning electron microscopy, and electrochemical performance measurements were studied. The results indicated that the prepared Li3V2(PO4)3/LiFePO4 (LVP/LFP) composite material exhibited better discharging capacity at high C rate and at low temperature than that of LFP and bulk LVP/LFP. This can pave an effective way to improve the performance of LFP at high C rate and at low temperature.